ADC for read battery level the event is not trigger in second time?

We are using nRF52840 SDK 15.0 with Segger embedded studio. We have referred ble_app_proximity example only for read battery level using ADC. Now in our application used SAADC for read 3 axis sensor data for that we have configured saadc_init(); For battery level read we have configured adc_configure_battery();

Meaning there are two function used for different ADC configuration, my saadc_init() function worked properly and also their saadc_callback(..) getting. But problem coming for adc_configure_battery() function event call back is not triggering means saadc_battry_event_handler() not trigger in second time.

I have called this function like 

void saadc_battry_event_handler(nrf_drv_saadc_evt_t const *p_event) {
  if (p_event->type == NRF_DRV_SAADC_EVT_DONE) {
    nrf_saadc_value_t adc_result;
    uint32_t err_code;

    err_code = nrf_drv_saadc_buffer_convert(p_event->data.done.p_buffer, 1);
    adc_result = p_event->data.done.p_buffer[0];
//    NRF_LOG_INFO("%d", adc_result);
    s_info.batt_lvl_in_milli_volts = ADC_RESULT_IN_MILLI_VOLTS(adc_result) +
    s_info.percentage_batt_lvl = battery_level_in_percentage(s_info.batt_lvl_in_milli_volts);
    err_code = ble_bas_battery_level_update(&m_bas, s_info.percentage_batt_lvl, BLE_CONN_HANDLE_ALL);
    if (
        (err_code != NRF_SUCCESS) &&
        (err_code != NRF_ERROR_INVALID_STATE) &&
        (err_code != NRF_ERROR_RESOURCES) &&
        (err_code != BLE_ERROR_GATTS_SYS_ATTR_MISSING)) {

/**@brief Function for configuring ADC to do battery level conversion.
static void adc_configure_battery(void) {
  ret_code_t err_code;
  nrf_saadc_value_t adc_battery_buf[2];
  NRF_LOG_DEBUG("adc_configure_battery call");
  nrf_saadc_channel_config_t config =

  err_code = nrf_drv_saadc_init(NULL, saadc_battry_event_handler);

  err_code = nrf_drv_saadc_channel_init(3, &config);

  err_code = nrf_drv_saadc_buffer_convert(&adc_battery_buf[0], 1);

  err_code = nrf_drv_saadc_buffer_convert(&adc_battery_buf[1], 1);

  err_code = nrf_drv_saadc_sample();

My battery level not updating when sensor device wake up then i called above functions to trigger adc_configure_battery(); event handler.

My question is any problem is i used two ADC configuration function?

2. Why battery event means saadc_battry_event_handler(); is not triggering?